Low energy gaseous fuels are an abundant source of cheap energy. These gases are released by coal mines and landfills and contain a quantity of hydrocarbon fuel, such as methane. Typically, these gases can contain as much as fifty percent hydrocarbon fuel, but some sources contain as little as thirty percent hydrocarbon fuel.
One use for this low energy gaseous fuel is to power an internal combustion engine. The internal combustion engine can be used to drive a generator to produce electricity. The electricity can then be fed into a power grid of an electric utility company in order to generate revenue, or alternatively the electricity can be fed to devices (e.g. lights, pumps, etc.) located proximate the generator in order to power such devices.
A drawback to using low energy gaseous fuels is that internal combustion engines that have heretofore been designed cannot be reliably run with fuels that have a hydrocarbon fuel content of less than forty five percent. In these engines, to combust a low energy gaseous fuel with a hydrocarbon fuel content of less than forty five percent, it is necessary to add natural gas, which has a higher energy content, to increase the energy content of the gaseous fuel. A disadvantage to adding natural gas to the low energy gaseous fuel is that natural gas is more expensive than the low energy gaseous fuel.
One objective when using an internal combustion engine is to reduce emissions of oxides of nitrogen (NO.sub.x) during operation thereof. NO.sub.x is produced when nitrogen and oxygen are combined at the high temperatures associated with combustion. Catalytic converters have been used with various internal combustion engines to control the emissions of NO.sub.x. A disadvantage to the use of catalytic converters is that catalytic converters cannot satisfactorily reduce emissions produced by internal combustion engines that combust low energy gaseous fuels. However, emissions can be reduced to a satisfactory level by precisely controlling the ratio of air to fuel combusted in the internal combustion engine.
What is needed therefore is an apparatus and method for controlling an internal combustion engine that uses a low energy gaseous fuel which overcomes one or more of the above-mentioned drawbacks.